The invention relates generally to machines or mechanisms for knotting the free ends of a coil spring to the adjacent end convolution of the coil spring.
Early knot-tying machines were powered and driven by a single camshaft assembly which was cyclically operated by a one-revolution mechanical clutch that was spring biased and pneumatically operated. The mechanical clutch was excessively noisy and caused excessive wear on the gears with every engagement.
Furthermore, the knot-tying or twisting member (to be described hereinafter) was driven from the camshaft by a partial gear, i.e., a gear which had only a limited arcuate range of teeth. This partial gear was removably fixed on the camshaft for periodic driving actuation of the knot-tying or twisting member. When it was desired to change the size of the knot, i.e., to vary the number of turns therein, it was necessary to at least partially disassemble the camshaft assembly to permit removal of one partial gear and then to reassemble the camshaft assembly with another partial gear. Such disassembly and reassembly resulted in appreciable machine down time and was also labor intensive. Thus, it was expensive to disassemble and reassemble the camshaft assembly to vary the number of turns in the knot.
U.S. Pat. No. 5,477,893 discloses a knot-tying machine that operates without the mechanical clutch and partial gear configuration. Rather, the knot-tying member is independently driven by a dedicated servo-motor that can be electrically controlled to vary the number of turns in the knot. The machine incorporates a coupling, which takes the place of the mechanical clutch and transfers power from the servo-motor to the knot-tying member. The coupling, known as a Schmidt Offset Coupling, is capable of maintaining the drive connection between the servo-motor and the knot-tying member, notwithstanding the variable misalignment of shafts due to the engaging and retracting of the knot-tying member. The Schmidt coupling therefore eliminates the excessive noise and wear commonly associated with the mechanical clutch and enables the independent drive of the knot-tying member.
The present invention provides a knot-tying mechanism having an alternative to the Schmidt coupling, which also permits the independent drive of the knot-tying member and eliminates the excessive noise and wear associated with the prior art mechanical clutch. Generally, the invention provides substantially all of the features of the knot-tying mechanism disclosed in U.S. Pat. No. 5,477,893, which is hereby incorporated by reference, but it incorporates a robust linkage in place of the prior art Schmidt coupling.
More specifically, the present invention provides a coil spring knotting machine including a frame and a camshaft mounted on the frame about an axis fixed relative to the frame. The camshaft supports a support member having thereon a knot-tying member mounted for rotation about an axis movable with respect to the frame. The camshaft also supports a free-wheeling rotating member. The machine further includes a first drive member rotatably driving the camshaft without causing rotation of the rotating member, and a second drive member rotatably driving the rotating member without causing rotation of the camshaft. A linkage connects the rotating member to the knot-tying member to rotate the knot-tying member. Preferably, the linkage includes a flexible member and a movable tensioning member for adjusting the tension in the flexible member.